Mercury

Notes

Mercury cycle © EPA

Natural mercury derives from the weathering of mercury-bearing rocks, volcano's and hydrothermal vents. It's industrial use includes electronics, light bulbs and thermometers. Within these products, mercury doesn't pose a health problem. However when vaporised into the air by factories producing these products, it can be deposited in soils, and be flushed through rivers towards the ocean. Once deposited in anoxic soils, mercury can be transformed by bacteria to methylmercury.

In the Northern hemisphere anthropogenic sources have largely been eliminated since the 1980's. Mercury is the only contaminant (apart from pathogens) that with certainty has been responsible for human deaths^[3]. In humans high levels of mercury can cause:^[4]

Disruption of the nervous system
Damage to brain functions
DNA damage and chromosomal damage
Allergic reactions, resulting in skin rashes, tiredness and headaches
Negative reproductive effects, such as sperm damage, birth defects and miscarriages

Concentrations of mercury on the open ocean range from 0,001 to 0,004 µg/l, in coastal areas concentrations are usually 10 times higher. In heavily polluted systems however (like the Targus estuary in Portugal or Minamata bay in Japan) concentrations have been as high as 80ng/l.

Although inorganic mercury doesn't have biomagnifying characteristics, the organic compound, methylmercury, does.